Method for operating a block model based field device for a distributed automation system

ABSTRACT

In a method for operating a field device working according to the block model for a distributed automation system, which exchanges data via a fieldbus, a first function block application serving for process control is provided, which makes available to other system participants process data via a first virtual field device object. In addition, a second function block application is provided, which serves for plant monitoring and which makes available to other system participants plant monitoring data via a second virtual field device object, wherein the first and second function block applications are executed according to different schedules.

The invention relates to a method, as defined in the preamble of claim1, for operating a field device working according to the block model fora distributed automation system.

Distributed automation systems are often applied in automationtechnology (manufacturing automation, or process automation) for plantcontrol. Serving for registering and/or influencing the processvariables relevant for the control are so-called field devices. Examplestherefor include fill level measuring devices, mass flow measuringdevices, pressure and temperature measuring devices, etc., which, assensors, register the corresponding process variables fill level, flow,pressure, or temperature.

Serving for influencing process variables are actuators, e.g. valves orpumps, via which the flow of a liquid in a pipeline section, or the filllevel in a container, can be altered.

A large number of such field devices are available from the members ofthe firm, Endress+Hauser.

For data exchange between the field devices and superordinated units(e.g. control systems, control units, etc.), fieldbus systems areapplied. The superordinated units serve for process control, processvisualizing, process monitoring and plant monitoring, as well as forstart-up and for servicing the field devices.

Also referred to as field devices are, generally, units, which areconnected directly to a fieldbus and serve for communication withsuperordinated units (e.g. I/Os, gateways, linking devices,controllers). Frequently, fieldbusses are also integrated in enterprisenetworks, which work on an Ethernet basis, in order that process, orfield device, information can be accessed from different regions of anenterprise.

For global communication, company networks can be connected with publicnetworks (e.g. Internet).

For servicing and for start-up of the field devices, correspondingoperating programs are necessary (e.g. FieldCare of Endress+Hauser;Pactware; AMS of Emerson; Simatic PDM of Siemens).

Serving for plant control of larger plants are control systemapplications (e.g. Simatic PCS7 of Siemens; Freelance of ABB; Delta V ofEmerson).

An essential aspect of open fieldbus systems (Profibus, FoundationFieldbus) is the interoperability and exchangeability of devices ofdifferent manufacturers. In a plant, devices (sensors, actuators, etc.)of different manufacturers can be applied together. In the case offailure of a sensor of a particular manufacturer, an option is tosubstitute for such a similar sensor of another manufacturer.

These requirements necessitate a clear structuring of data and functionsin the individual field devices, in order to enable unified accessing.This is achieved through a standardized block model, which underliesboth of the fieldbus systems, Profibus and Foundation Fieldbus.

Data and functions of a field device are, in such case, encapsulated indifferent blocks, which appear externally as communication objects. Eachfield device working according to the block model includes at least onedevice block (resource block), which provides all data identifying adevice, e.g. device manufacturer name, serial number, hardware, andcompany, versions, etc. In addition to the device block, there is atransducer block, which serves for conditioning signals. As a rule, thesignals are raw signals (input signals), which come from a measuringtransducer and must be conditioned, before they can be fed to additionalfunction blocks. In the transducer block, there occurs a calibrating anda linearizing of the raw signal, so that the actual measured value isavailable as output signal of the transducer block. A large number ofpredefined, basic function blocks are made available. Typical functionblocks are: Analog input, analog output, digital input, digital output,PID controller, etc. These function blocks are combined to form acontrol strategy in the field devices with the assistance of acorresponding operating tool, e.g. ControlCare of the firm,Endress+Hauser. The so created control strategy serves exclusively forthe process control.

Serving for plant monitoring (asset management) are, as a rule,corresponding application programs, which likewise run on thesuperordinated units.

Process control and plant monitoring are, most often, two completelyseparate systems. Data exchange between these systems is onlyimplemented with considerable effort.

An object of the invention is, therefore, to provide a method foroperating a field device of automation technology working according tothe block model, such that an easy data exchange between a processcontrol system and a plant monitoring system is enabled.

This object is achieved by the features set forth in claim 1.

Advantageous further developments of the invention are set forth in thedependent claims.

An essential idea of the invention is to provide two virtual fielddevice objects in a field device, wherein the one virtual field deviceobject is connected with a function block application serving forprocess control and the other virtual field device object is connectedwith a second function block application serving for plant monitoring.The two function block applications are executed on different schedules.Since, for plant monitoring, function block applications withcorresponding function blocks are used, an easy data exchange betweenprocess control systems and plant monitoring systems is possible.

The invention will now be explained in greater detail on the basis of anexample of an embodiment illustrated in the drawing. The figures of thedrawing show as follows:

FIG. 1 distributed automation system in schematic representation;

FIG. 2 field device of a distributed automation system of FIG. 1;

FIG. 3 function block application in a field device of FIG. 2 inschematic representation;

FIG. 4 function block application according to FIG. 3 with differentinterfaces; and

FIG. 5 block diagram of a field device of FIG. 1.

FIG. 1 shows a distributed automation system VS in greater detail.Connected to a data bus D1 are a number of computer units (workstations)WS1, WS2, WS3. These computer units serve as superordinated units, amongother things, for process visualizing, process monitoring and forengineering, as well as for servicing and monitoring of field devices.Data bus D1 works, for example, according to the HSE (High SpeedEthernet) standard of Foundation Fieldbus. Via a linking unit V1, thedata bus D1 is connected with a fieldbus segment SM1. The linking unitV1 can be, for example, a control unit (FieldController of the firm,Endress+Hauser). The fieldbus segment SM1 is composed of a plurality offield devices F1, F2, F3, F4, which are connected with one another via afieldbus FB. The field devices F1, F2, F3, F4 can be sensors, as well asalso actuators. Fieldbus FB works, for example, according to thefieldbus standard of Foundation Fieldbus.

FIG. 2 shows, schematically, one of the field devices, for example,field device F1. The physical connection of the field device F1 with thefieldbus occurs via an interface PHY, which is embodied as a fieldbusinterface. This fieldbus interface adapts the physical signal to theused fieldbus standard. The protocol specific adapting occurs in acommunication stack (communication stack) ST. This communication stackST is connected with a plurality of virtual field device objects(virtual field devices). These virtual field device objects makeavailable all communication objects and their object descriptionstransmittable via the fieldbus. One virtual field device object is thenetwork and system management object NSM VFD connected with a networkand system management application NSMA. Another virtual field deviceobject is the object VFD1, which is connected with a function blockapplication FBA1. These objects and applications are known in the caseof conventional field devices.

According to the invention, a further virtual field device object VFD2is provided in the field device F1, which is connected with a functionblock application FBA2.

Function block application FBA1 serves for process control. Functionblock application FBA2 serves for plant monitoring.

These two function block applications are in FIG. 3 presented in greaterdetail. The virtual field device object VFD2 is connected with a plantmonitoring function block AFB and a diagnostic function block DIAG FB.With the help of the diagnostic function block DIAG FB, device-specificdiagnostic information is queried, or ascertained. The plant monitoringfunction block AFB processes plant monitoring relevant information. Bothof these function blocks are so called flexible function blocks, forwhich Foundation Fieldbus has created corresponding specifications.

The virtual device-object VFD1 is connected with a conventionalstandardized AI function block AI FB. The AI function block AI FB isconnected with a PID controller function block PID FB. Moreover, in theview of the function block application FBA1, the plant monitoringfunction block AFB can be seen; therefore this is shown dashed. Dataexchange between the diagnostic function block DIAG FB and the controlfunction block PID FB is also shown dashed. The plant monitoringfunction blocks AFB and DIAG FB are implemented according to IEC61131-3programming and are executed in the function block environment madeavailable by the field device F1. In this way, an easy exchange betweena process control system and one in the plant monitoring system ispossible. The differentiating of plant monitoring and process dataalready at the field device level makes possible an easy data exchange.If the field device F1 is, for example, a pH electrode and thediagnostic function block DIAG FB reports that the pH electrode isfouled, then this information is forwarded to the PID controllerfunction block, which then switches the PID control function block PIDFB into a safety mode, since, in this case, safe operation of the plantis possibly no longer assured. Corresponding connections between thefunction blocks can be effected simply with conventional operatingtools.

FIG. 4 shows an alternative embodiment of the invention. In such case,the virtual field device objects VFD1, VFD2 access differentcommunication interfaces. The communication blocks of the conventionalvirtual field device object VFD1 are, in ordinary manner, made availableto other system participants via the fieldbus FB. The second virtualfield device object VFD2 is connected with a radio interface PHY', whichexchanges data wirelessly with other system participants. Thus the plantmonitoring relevant data are transmitted on a completely differentcommunication channel. This unloads the data transmission rate on thefieldbus FB.

The transmission on this communication channel can also occur accordingto another protocol. This is indicated by the communication stack ST′.

Depending on application of the function block sets (process control,plant monitoring), memory ranges and logical data structures can bedynamically assigned. If only plant monitoring functions are required,then the entire available memory capacity can be assigned to thesefunctionalities.

Included under plant monitoring is also state monitoring in the contextof condition monitoring.

FIG. 5 shows the hardware related construction of the field device F1 ingreater detail. A microcontroller μC is connected with a measuringtransducer MA, which serves for registering a process variable, e.g. apH value. Connected to the microcontroller μC are a number of memoryunits. A memory VM serves as temporary, volatile, working memory.Serving as program memory for the microcontroller μC is EPROM memory orflash memory. In a non-volatile, writable, data memory NVN, e.g. anEEPROM memory, are stored parameter values. For measured value displayand for servicing, a display/service unit AB is provided, which includesa display and a number of pushbuttons.

Serving for communication with the fieldbus is communication controllerCOM, after which a fieldbus interface PHV is connected. Thecommunication stack, or stacks, is/are implemented in the communicationcontroller COM.

Serving for energy supply of the device is a supply part VT, whicheither is connected with an external supply unit or draws its energyfrom the fieldbus FB via the fieldbus interface PHY.

1-5. (canceled)
 6. A method for operating a field device workingaccording to a block model for a distributed automation system thatexchanges data via a fieldbus, comprising the steps of: providing afirst function block application, which serves for process control andwhich makes available to other system participants process data via afirst virtual field device object; and providing a second function blockapplication which serves for plant monitoring and which makes availableto other system participants plant monitoring data via a second virtualfield device object, wherein: the first and second function blockapplications are executed according to different schedules.
 7. Themethod as claimed in claim 6, wherein: the second function blockapplication includes a diagnostic function block, which registersdevice-specific, diagnostic information.
 8. The method as claimed inclaim 6, wherein: the second function block application includes a plantmonitoring function block, which provides plant monitoring information.9. The method as claimed in claim 6, wherein: a function block of thefirst function block application and a function block of the secondfunction block application exchange data.
 10. The method as claimed inclaim 6, wherein: the first and second virtual field device objects areconnected with different interfaces and/or communication stacks.